Endoscope with a movable frontal end area

ABSTRACT

An endoscope comprising an endoscope shaft (2) having in the front end portion a movable section, with the endoscope shaft (2) having provided therein at least one miniaturized electric drive member (22) for moving the movable section (4).

The invention relates to an endoscope comprising an endoscope shafthaving a movable section in the front to end portion.

Endoscopes have become an important auxiliary means in technology andmedicine for inspecting channel-like cavities that are not accessible indifferent manner or with considerable operations only. Endoscopes areequipped at their distal ends with an illumination means and an opticalsystem for visually inspecting the cavity region in front thereof. Theoptical information detected at the distal end in the front portion ofthe endoscope is normally transmitted either by a fiber optical systemthrough the endoscope shaft rearwardly to its operating end, or isdetected at the distal end by a camera chip and transmitted back by anelectrical line through the endoscope shaft and made visible on a screenmonitor. Endoscopes on the whole, apart from the rear operating end,usually have an elongate, flexible rod-like configuration.

A movable section in the front end portion of the endoscope providesenhanced possibilities in inspecting a channel-like cavity. In case ofcommercially available endoscopes, the movable section can be bent,especially for obtaining a frontal position of the wall portion of thecavity to be examined in front of the endoscope shaft end. Commerciallyavailable endoscopes are formed on their rear operating ends withrotatable wheels through which bending of the movable section can beeffected by means of Bowden wires. Working with such rotatable wheels isquite inconvenient. In particular with relatively long endoscope shaftsor with endoscope shafts located in bends during use, the considerablefriction of the Bowden cables renders finely tuned and exact bending ofthe movable section more difficult.

The endoscope according to the invention is characterized in that theendoscope shaft has at least one miniaturized electric drive memberprovided therein for moving the movable section.

The electrical movement of the movable section according to theinvention permits working in much more convenient and finely tunedmanner. Due to the fact that the driving movements are transmitted tothe movable sections via shorter distances, the problems in connectionwith friction are decreased. In addition thereto, those problems areeliminated that are connected with an exact transfer of movement by theBowden wire across larger distances, in particular the empty run due toplay of the Bowden wire in its enclosure, tendency to make the Bowdenwire enclosure shorter and straight, and the like.

The at least one miniaturized electric drive member is providedpreferably in the vicinity of the movable section of the endoscopeshaft. This kind of expression also is to comprise the situation thatthe drive member is accommodated virtually directly adjacent the rear ofthe movable section, and even in the movable section itself. However, italso is to comprise the situation that the drive member is spacedrearwardly a certain distance from the movable section. However, thisdistance should not be too large so that the problems outlined in thepreceding paragraph do not become too prominent.

It is preferred to use a piezoelectric drive member as miniaturizeddrive member. There are piezoelectric crystals and ceramics which changetheir length when a voltage is applied thereto. For practicalapplication, a plurality of thin piezoelectric crystal or piezoceramicplatelets is stacked onto each other with a conductive layer beingapplied between successive platelets. When a voltage is applied betweentwo successive conductive layers each, e.g. an expansion of the stack ofpiezo-platelets in the longitudinal direction thereof results in case ofa corresponding orientation of the piezoelectric material. Suchpiezoelectric elements may produce very high setting forces in relationto the size thereof.

Due to the fact that the expansion in length upon application of thevoltage is only about 1 per mil of the length of the piezo-material, anadvantageous possibility consists in producing the necessary settingmovements by way of a sequence of linear driving steps.

There are cases in which the drive member can be placed only withdifficulty at that location where the driving movement for moving themovable section is necessary. In a development of the invention it isthus preferred to provide a motion transmitting member between the drivemember and the movable section. The motion transmitting memberpreferably is an elongate, flexurally stiff or flexurally soft strand.Moreover, it may be preferred to provide as motion transmitting member aflat strand of arbitrary width. As concrete examples in this respect,rope-like tensile members and members in the form of especially thinrods or bands are indicated, with metallic materials, plasticsmaterials, fiber-reinforced materials as well as many other materialsbeing feasible in this respect. The drive member acts on the motiontransmitting member and the latter is connected to the movable sectionof the endoscope shaft.

The endoscope preferably has a position determining means fordetermining the position of the motion transmitting member with respectto its longitudinal movement in relation to the drive member.

If, as elucidated in still more detail hereinafter, a plurality of drivemembers is accommodated in the endoscope shaft in circumferentiallyspaced manner, in particular to be able to shorten or lengthen and bendthe movable section, the respectively associated drive members due tothe position determination of the motion transmitting members can becontrolled such that the motion transmitting members are all identicallymoved in forward direction or in rearward direction, i.e. the movablesection of the endoscope shaft is lengthened or shortened in rectilinearmanner. Moreover, due to the position determination, electricalinformation is present as to whether or not the movable section isreally aligned in rectilinear manner. In case of bending of the movablesection, a proper operation is ensured. For, a drive member operating inpulling direction, because a bending resistance of the movable sectionhas to be overcome, provides a lower bending speed of the motiontransmitting member than a drive member operating in pushing or outwarddirection for the convex side of the bend. Due to the position detectionof the motion transmitting members, the drive members can be controlledfor the bending operation such that, on the concave bending side, themovement member or members can be pulled rearwardly with anappropriately corresponding speed as, on the convex side of the bend,the motion transmitting member or members are pushed forwardly. On caseof bending of the movable section, electrical information is alsopresent as to the actual bending condition, which may be made visiblefor the examining doctor on a display. The aforementioned control of thedrive members with respect to specific required speeds takes placepreferably by controlling the frequency of the course of movements ofthe particular drive member.

The position determining means is provided preferably in the form of aposition determining means operating on the basis of induction. Thelatter can be realized in particular in the form of a coil into whichthe motion transmitting member or a specific portion of the motiontransmitting member is axially immersed to a larger or lesser extent. Bymeasuring the instantaneous inductance of the coil, it is possible todetermine the immersion length of the motion transmitting member or ofthe portion of the motion transmitting member and thus the position ofthe same as regards its longitudinal movement relative to the drivemember.

It is particularly advantageous when the position determining means hastwo coils disposed on both sides of the drive member. Further details onthis development will be indicated hereinbelow in connection with thepreferred embodiments.

The drive member during operation thereof develops a heat loss.Especially with a piezoelectric drive member, the temperature thereofdue to the heat loss may increase to such an extent that thepiezo-effect necessary for its function is deteriorated. It is thereforepreferred in a further development of the invention to provide a coolingmeans for the at least one drive member. The cooling means inparticularly advantageous manner may be provided in the form of anevaporation bath cooling means, using e.g. an inert liquid such asliquid fluorocarbon boiling at a temperature such as e.g. 50° C., whichis below the temperature of the considerable degradation of thepiezo-effect. The evaporation bath cooling provides a particularintensive heat transition from the piezoelectric components by localevaporation of the cooling liquid. The vapor bubbles created therebycondense in the cooling liquid at some distance from the cooling sitesproper. Due to the fact that the absolute power dissipations to bedissipated by cooling are quite low, no excess heating of the coolingliquid in total results.

The afore-mentioned evaporation bath cooling can be effected very easilyby filling the inside of the endoscope shaft with the cooling liquid atleast in that portion where the drive member or members are disposed.Cooling liquids of the type mentioned furthermore have excellentinsulating properties so that the insulating expenditure for the drivemember can be kept low. Finally, it is advantageous for closelyobserving the fit for the clamping operation between the drive memberand the motion transmitting member when, due to said cooling, the drivemember is operated in a relatively narrow temperature range.

The drive member preferably is to be equipped with two piezoelectricallyoperable clamping members for alternating engagement with the motiontransmitting member. By lining up activating means of the two clampingmembers and the piezoelectric linear mover, relative movement betweenmotion transmitting member and drive member is produced. The term"relative movement" means that on the one hand the drive member may movealong a stationary motion transmitting member and that on the other handthe motion transmitting member may be displaced by a fixed drive member.

In a preferred development of the invention, the clamping membercomprises at least one clamping engagement body, and the piezoelectricactuating movement is converted via an inclined surface into theclamping movement of the clamping engagement body. Depending on theextent of inclination of the inclined surface relative to the workingdirection of the piezoelectric clamping member actuator, a forceamplification for clamping the motion transmitting member or anincreased distance for the clamping movement of the clamping engagementbody can be produced purposefully. Preferably several clampingengagement bodies are provided clamping the motion transmitting membertherebetween; when only one clamping engagement body is provided, thelatter clamps the motion transmitting member against an abutment.

It is favorable when, upon termination of the actuation of the clampingmember, the clamping engagement is resiliently released again. Theclamping member may be an integral part or be composed of several parts.

In a further preferred development of the invention, the respectiveclamping member has at least one clamping engagement body inclinedrelative to the motion transmitting member, said body being arrangedsuch that it pivots under the effect of the piezoelectric actuatingmovement and is brought into clamping engagement with the motiontransmitting member. In an idealized clamping member, the clampingengagement body is pivoted about a fixed pivot. Depending on the extentof inclination and the distances between pivot and clamping surface onthe one hand and pivot and the location where the piezoelectricactuating movement engages the clamping engagement body, on the otherhand, it is possible, by a leverage effect, to purposefully produce aforce amplification for clamping the motion transmitting member or anincreased distance for the clamping movement. For the force transferbetween clamping member actuator and clamping engagement body, there maybe provided at least one flexible connection. The connection betweenclamping member actuator and clamping engagement body preferably isprovided in flexurally soft, integral manner. As an alternative thereto,it is also possible to provide a caliper member freely abutting on oneside.

Furthermore, it is possible to provide such an inclination of theclamping engagement body with respect to the motion transmitting memberthat a self-amplification of the clamping engagement results when forceis transmitted between the clamping member and the motion transmittingmember. In terms of function, the acute angle between the longitudinaldirection of the motion transmitting member and that straight line is ofimportance which extends from the clamping surface of the clampingengagement body to the virtual pivot of the latter during the clampingmovement, irrespective of the geometric design of the clampingengagement body. There is a borderline angle as of which theself-amplification commences; the operating force of the clampingactuator and the force from the self-amplification cooperate forproducing the clamping engagement. In case of a still acuter angle, apoint is reached as of which the operating force of the clampingactuator is still needed only for producing an initial clampingengagement; the force from the self-amplification alone can ensure thefurther clamping engagement.

The inclined surface as mentioned several times hereinbefore may beprovided on the clamping engagement body and/or a component cooperatingtherewith.

It is particularly advantageous to arrange the piezoelectric componentsof the piezoelectric drive member all on one side of the motiontransmitting member. Such an arrangement provides the advantage that thesize of the piezoelectric drive member--in particular its width orheight, respectively,--can be reduced considerably. It is thusconsiderably easier to accommodate several drive members at the samelocation with respect to the longitudinal extension thereof in theendoscope shaft. In addition thereto, this construction provides aconsiderable simplification with respect to the manufacture of the drivemembers.

The construction of the drive member is particularly simple when theself-amplification effect is utilized only in one of the twolongitudinal movement directions of the motion transmitting member. Inspecific applications, when especially large forces in one of these twomovement directions are to be produced, it is advantageous to arrangeboth clamping members "in the same direction".

It is most advantageous when the clamping member has several clampingengagement bodies distributed across its circumference. A motiontransmitting member, at least for part of its circumference, may then begrasped and clamped by the same as by clamping pliers or by a drillchuck.

A design of a clamping member that is preferred as it is especiallysimple for practical application is provided by a ring member that isslotted, in particular along part of its length.

The technical realization is particularly easy when the motiontransmitting member is an elongate strand. In this respect, severalsolutions are conceivable, and e.g. a tensile rope of metal or plasticsor also a rod adapted to transfer pulling and/or pushing forces may beemployed for transmitting the movement.

A good compromise between a large number of movement possibilities andconstructional expenditure is provided by arranging three drive membersin circumferentially spaced apart manner in the endoscope shaft; themovable section can thus be bent in any direction. When the movablesection is formed in one region to be invariable in length, it is alsopossible to make do with just two drive members; however, in that casethe motion transmitting members must also be capable of transmittingpushing forces.

It is possible to provide several drive members beside each other, whichwith respect to the longitudinal extension of the endoscope shaft aredisposed substantially at the same location. As an alternative theretoit is possible to provide several drive members disposed in staggeredmanner in the longitudinal direction of the endoscope shaft. This isappropriate especially in such cases in which, if they were arrangedsubstantially at the same location in the endoscope shaft, only littlespace would be left for the passage of the working channel or if, due tothe size of the working member, an arrangement substantially at the samelocation of the endoscope shaft would not be possible.

The two most important movement possibilities of the movable section,which are preferred according to a development of the invention, arebendability and length variability. For more thorough inspection, thelatter allows a very purposeful movement towards a portion of the cavitywall to be inspected. Both posibilities of movement may also becombined.

The invention may be utilized on the one hand for inspection but on theother hand also for performing operations in technical plants andequipment. Nuclear reactors, chemical plants, piping systems are to benamed just as a few of the numerous examples. On the other hand, theinvention may be employed advantageously in the medical field, inparticular for the exploration of cavities or tubular channels of thehuman body or for performing minimum invasive operations. Endoscopeshave become established in particular for the exploration of oesophagus,stomach, duodenum from the stomach, intestine from the anus, urethra,bladder and ureters. Endoscopes as a rule have a so-called workingchannel through which various working utensils can be introduced, e.g.small pliers for taking tissue samples, biopsy needles, heatable cuttingwires, small scissors, coagulation electrodes or the like. It is to bepointed out here that some of the working utensils, similar to themovable section of the endoscope, may be operated by miniaturizedelectric drive members. Finally, there is provided as a rule a fluidchannel for rinsing liquid, which may also be used for inflating withair or specific gases. The term "endoscope" in its entirety in thepresent application is to comprise also such apparatus in which theaspect of an optical inspection is not in the foreground.

The invention provides the great advantage that the friction along themotion transmitting members of an endoscope, especially when used inhighly looped channel-like cavities, can be largely eliminated so thatthe movable section of the endoscope in advantageous manner can bepositioned very exactly. The use of an endoscope thus is not impaired bythe length and shape of the cavity to be inspected, which is importantin particular for the exploration of the human rectum, large intestineand small intestine as well as for difficult applications in loopedcavity systems.

Control of the drive members and the front section of the endoscope,respectively, takes place e.g. by means of a joystick and an electroniccontrol system in precise manner and requires less attention. This has abeneficial effect on the person performing the examination who no longerhas to use his concentration for positioning, but can concentrate fullyon the examination of the cavity.

Another great advantage consists in the length variability in the regionof the movable section through which the front end of the endoscope canbe moved to a portion of the cavity wall to be examined. This isimportant especially in such cases in which, e.g. for coloscopy, thewall has a very irregular structure. When, for example, additionalworking utensils are introduced in this case through a working channel,the close movement to the wall portion to be operated upon reduces therisk of causing injury to a non-involved wall portion by the workingutensil.

An additional subject matter of the invention is a miniaturized,electrical linear drive member for an endoscope having a movable sectionin the front end portion of the endoscope shaft, characterized in thatit is a piezoelectric drive member comprising a piezoelectric linearmover and two piezoelectrically operating clamping means to be activatedin alternating manner for providing a clamping engagement with an objectmovable by the linear drive member.

It is stressed emphatically that this linear drive member according tothe invention is not only usable for moving the movable section of anendoscope shaft, but in all cases where miniaturized, electric drivemembers are useful. The scope of the invention thus includesminiaturized, electric linear drive members of the type defined in thepreceding paragraph for arbitrary fields of application.

It is emphasized furthermore that all more specific design features thatare useful for the drive member--although they may be described inconnection with the endoscope--may also be provided in the linear drivemember when intended for other applications than the endoscopes, eitherindividually or in combination of several features.

With respect to the linear drive member mentioned somewhat earlier,reference was made to "an object movable by the linear drive member"instead of the motion transmitting member, since in other fields ofapplication than the endoscope, a motion transmitting member in thestrict word sense often is not present.

The invention and developments of the invention shall be elucidated inmore detail hereinafter by way of a partly schematic representation ofan embodiment in the drawings wherein

FIG. 1 shows a partly sectional view of the front end portion of anendoscope according to the invention;

FIG. 2 shows, in an enlarged scale, a longitudinal section of apiezoelectric drive member, with the lower half showing a firstvariation and the upper half showing a second variation;

FIG. 3 schematically shows a sequence of movement steps causing adisplacement of the motion transmitting member in a piezoelectric drivemember according to FIG. 2;

FIGS. 4, 5 and 6 show respectively longitudinal sections of a part ofthe engagement portion between a clamping member and a motiontransmitting member;

FIG. 7 shows a side view, partly in longitudinal section, of analternative embodiment of a piezoelectric drive member;

FIG. 8 shows a cross-section through the drive member along line 8--8 inFIG. 7;

FIG. 9 shows a cross-section through the drive member along line 9--9 inFIG. 7;

FIG. 10 shows a schematic view of a drive member having an associatedposition determining means.

FIG. 1 shows part of an endoscope shaft 2 having a semi-stiff, flexiblemain section 6 and a movable section 4 in the front end portion. Movablesection 4 is constituted in essence by a supporting member coated withelastic material 10, e.g. rubber. Supporting member 10 may be formed inthe manner of a helical spring. Movable section 4 is closed at its frontend 8. Front end 8 accommodates therein a camera chip 12 detectingoptical information and transmitting it to the rear via an electricalline 14 extending through the endoscope shaft. Three motion transmittingmembers 16, 18, 20 are attached at front end 8 close to thecircumference in circumferentially distributed manner spaced apart by anangular distance of 120°. The motion transmitting members 16, 18 and 20,behind the transition 28 between movable section 4 and main section 6 ofthe endoscope shaft, are each engaged with a miniaturized piezoelectricdrive member 22, 24, 26 and extend beyond the latter a certain distanceto the rear. A widened portion 27 is provided at the rear end of eachmotion transmitting member 16, 18, 20 in order to prevent furthermovement through the drive members 22, 24, 26.

Drive members 22, 24, 26 are secured in main section 6 of endoscopeshaft 2 shortly before transition 28 and have power supplied thereto viaelectrical lines 30, 32 and 34. In the embodiment shown, drive members22, 24, 26 are disposed close to transition 28 substantially with thesame distance from the latter, but they may also be arranged instaggered manner in the longitudinal direction.

When one of the drive members 22, 24, 26 effects shortening of theassociated motion transmitting members 16, 18, 20, bending of themovable section 4 is caused in the axial plane containing the particularmotion transmitting member. When a pulling force is applied to severalmotion transmitting members simultaneously, the direction of bendingresults in the form of a vectorial superimposition. By cooperativeactuation of the drive members 22, 24, 26, the movable section 4 thusmay be curved into any direction desired.

In addition to camera chip 12, a working channel may terminate at frontend 8 of the endoscope shaft, into which working utensils may beintroduced from the rear end of the endoscope shaft, with this channelbeing not shown in FIG. 1.

Drive member 22 shown in FIG. 2 consists in essence of a first clampingmeans 38 (on the right-hand side in FIG. 2), a second clamping means 40(on the left-hand side in FIG. 2) and a piezoelectric linear mover 36disposed therebetween. These three components, roughly speaking, areeach of hollow cylindrical configuration and disposed coaxially oneafter the other. Drive member 22 has in total four plates, namelyadvancing from the right to the left in FIG. 2, a first plate 41disposed at the end, a second plate 43 between first clamping means 38and linear mover 36, a third plate 45 between linear mover 36 and secondclamping means 40, and a fourth plate 47 at the left-hand end. Plates41, 43, 45, 47 extend at right angles to the longitudinal axis 49 ofdrive member 22.

The motion transmitting member 16 of circular cross-section extendslongitudinally through a central channel of drive member 22.

Clamping means 38 and 40 are of identical construction so that it issufficient to describe only first clamping means 38 hereinafter.

First clamping means 38 consists in essence of a piezoelectric clampingmember actuator 44 and a clamping member 48 of in total circularconfiguration. Clamping member actuator 44 consists of a stack ofpiezoelectric discs supported on its left-hand side in FIG. 2 on secondplate 43. Clamping member 48 is slotted along more than half of itsaxial length by a plurality of circumferentially distributed slots sothat a plurality of finger-like clamping engagement bodies 51 is formed,each having a clamping surface 56 on the radial inside. Clamping member48 is supported with its right-hand face side on first plate 41.

First plate 41 and second plate 43 are connected to each other by aplurality of axially extending screws 52 distributed around longitudinalaxis 49.

When clamping member actuator 44 is activated by supply of currentthereto, its right-hand face side in FIG. 2 moves towards the right; adisc 50 located in front of the same is pressed against outer inclinedsurfaces 54 of all clamping engagement bodies 51 and moves the clampingsurfaces 56 thereof substantially radially inwardly, so that theseclamping surfaces 56 come into clamping, frictional engagement with theouter circumference of motion transmitting member 16.

When clamping member actuator 44 is deactivated, clamping engagementbodies 51 due to their inherent elasticity move back into their radiallyouter initial position.

Second clamping means 40 is oriented in the same direction as firstclamping means 38. The stationary face side of clamping member actuator44 of the second clamping means 40 thus is supported on fourth plate 47,and clamping member 48 of second clamping means 40 is supported with itsstationary face side on third plate 45.

Between second plate 43 and third plate 45, linear mover 36, which isagain in the form of a stack of piezoelectric discs, is disposed withoutplay. Linear mover 36 is clearly longer in axial direction than clampingmeans 38 and 40. In case of the variation shown at the top in FIG. 2,second plate 43 and third plate 45 are connected to each other by aplurality of screws 53 distributed around longitudinal axis 49. Screws52 mentioned hereinbefore as well as screws 53 may be uniform threadedrod-like components that are continuous over the entire length of drivemember 22. In case of the variation shown at the bottom in FIG. 2,screws 53 are missing. In this variation, the face ends of linear mover36 are fixedly connected to the respectively associated plate 43 and 45,respectively, whereas in the case shown in FIG. 2 at the top no fixedconnection is necessary there. In case screws 53 are provided, they aredimensioned in their diameter such that they expand upon activation oflinear mover 36 and thus permit movement apart of second plate 43 andthird plate 45; upon deactivation of linear mover 36, an elasticcontraction of screws 53 takes place. In contrast thereto, screws 52 ofclamping means 38, 40 are designed such that they do not expandsignificantly in axial direction upon activation of clamping memberactuator 44; a certain expansion of screws 52 is not harmful.

The linear actuation movement of a clamping member actuator 44 is about1/1000 of the length of the piezoelectric material in clamping memberactuator 44. The distance for moving clamping surfaces 56 of clampingmember 48 towards each other upon activation of clamping member actuator44 is dependent upon the axial length of the piezoelectric material inclamping member actuator 44 and upon the inclination of inclinedsurfaces 54 with respect to longitudinal axis 49.

FIG. 3 indicates a sequence of movement steps I to VI causing movementof the motion transmitting member 16 through drive member 22. Iindicates the clamping means 38, 40 and the piezoelectric linear mover36 of schematically shown drive member 22. Drive member 22, in theregion of clamping means 38, is fixedly connected to main section 6 ofthe endoscope shaft, which is not shown in FIGS. 1 and 2 but isindicated in FIG. 3 by the hatched portion. This fixed connection may beestablished e.g. by attachment to one or both of plates 41, 43.

In position I, clamping means 40 is in frictional engagement with motiontransmitting member 16, linear mover 36 has no voltage applied thereto,and clamping means 38 is not actuated. Upon actuation of linear mover36, the latter experiences a linear movement--shown in an enlargedscale--and thus displaces clamping means 40 in relation to fixedclamping means 38. This displacement of clamping means 40 also pullsmotion transmitting member 16 towards the left. This condition is shownin position II. A further linear displacement of motion transmittingmember 16 to the left can be carried out only after linear mover 36relative to motion transmitting member 16 has moved back again to itsinitial position. This requires a number of clamping operations shown inpositions III and IV. Fixed clamping means 38 is activated and thusfrictionally connected to motion transmitting member 16. Clamping means40 is then deactivated; deactivated linear mover 36 returns to itsoriginal shortened portion. From position V now reached, it is againnecessary to perform two re-clamping steps of clamping means 40 and 38,namely closing of clamping means 40 and opening of clamping means 38 forreaching starting position I again, whereafter a further displacement ofmotion transmitting member 16 is carried out in a new sequence of steps.

The setting operations of the piezo-members 36, 44 concerned take placevery rapidly so that a repetition of this step sequence provides asufficiently high setting speed for motion transmitting member 16.

When the sequence of movement steps I to VI takes place in the oppositeorder, motion transmitting member 16 is moved from the left to theright, instead of from the right to the left as described. Forconverting this movement into a movement of the end 8 of movable section4, either the motion transmitting member must be designed so as to becapable of transmitting pressure forces, or a resilient movement apartof supporting member 10 has to furnish the necessary movement force,with the motion transmitting member having the effect of a kind ofcontrolled brake.

As was already described hereinbefore, shortening of one of motiontransmitting member 16, 18, 20 by its associated drive member 22, 24, 26results in bending of movable section 4 with respect to main section 6of endoscope shaft 2. When all three motion transmitting members 16, 18,20 are shortened by the same length, this results in a linear decreaseof movable section 4. When such shortening of movable section 4 ofendoscope shaft 2 takes place against the spring force of the supportingmember of movable section 4, movable section 4 can be moved forwardly intelescope-like manner by release of the motion transmitting members 16,18, 20. The combination of bending movement and length variation permitsexact positioning of front end 8 of movable section 4 of endoscope shaft2 with respect to a wall portion of the cavity to be examined.

FIG. 4, in a still enlarged scale, illustrates the geometry of clampingmember 48 of FIG. 2 and its engagement portion with ring 50. Before thefinger-like clamping engagement bodies 51 merge with the unslottedportion of ring-like clamping member 48, they have a portion 58 ofrelatively low radial thickness. The elastic deformation of clampingengagement bodies 51 upon closure and opening takes place in essence insaid portion 58. A straight line is drawn through a representativecentral point 64 of portion 58 and a representative central point 66 ofclamping surface 56. Straight line 62 forms with longitudinal axis 49 orthe circumferential surface of motion transmitting member 16 an angle 60having such an extent that a self-amplification of the clampingengagement results. This self-amplification is active in one axialdirection only, namely upon displacement of motion transmitting member16 to the right in FIG. 4 by axial displacement of clamping means 48 tothe left in FIG. 4, or--when seen differently--when motion transmittingmember 16 is subjected to an external pulling force towards the right inFIG. 4. By means of clamping member actuator 44, only such a radialpressing force has to be applied via ring 50 and inclined surface 54 tothe circumferentially distributed clamping engagement bodies 51 that aninitial frictional force is created between clamping surfaces 56 and theouter circumference of motion transmitting member 16. When clampingmember 48 is then shifted in axial direction towards the left in FIG. 4,the pressing force acting on clamping surfaces 56 is self-amplifying, sothat in principle forces of arbitrary magnitude can be transmitted inaxial direction between clamping member 48 and motion transmittingmember 16.

When the self-amplification effect described is of no great importancein a specific application, the two clamping means 38 and 40 may bearranged as mirror images of each other instead of in the same directionas shown in FIG. 2.

FIGS. 5 and 6 show that it is possible by selection of the angle 68between inclined surface 54 of clamping engagement bodies 51 of clampingmember 48 and longitudinal axis 49 or the circumferential surface of themotion transmitting member 16, respectively, to decide either for anincrease of the substantially radially extending pressing distance ofclamping surface 56 or for an increase of the radial pressing force ofclamping force 56. In case angle 68 is 45°, both the pressing distanceand the pressing force of clamping surface 56 correspond to the axialdistance and the force of clamping member actuator 44 applied in axialdirection. If, in contrast thereto, angle 68 is smaller than 45° (cp.FIG. 5), an increase in pressing force is obtained as compared to theforce delivered by clamping member actuator 44 and acting in axialdirection, of course with the sacrifice of a reduction of the movementdistance of clamping surface 56 as compared to the movement distance ofring 50 in axial direction.

If, however, angle 68 is greater than 45° (cp. FIG. 6), an increase inmovement distance substantially traveled in radial direction by clampingsurfaces 56 upon activation of clamping member actuator 44, as comparedto the movement distance of ring 50 in axial direction. However,concomitantly therewith, the radial pressing force decreases as comparedto the force delivered by clamping member actuator 44 in axialdirection.

FIGS. 5 and 6 again illustrate that the finger-like clamping engagementbodies 51, upon clamping and release thereof, perform a pivoting motionsubstantially around representative point 64.

In FIGS. 4, 5, 6, the bore of ring 50 is drawn such that its wall isinclined in conformity with the inclination angle of inclined surface54. This is not a cogent design. What is necessary is just that the boreof the ring is in engagement with inclined surface 54 in technicallysensible manner. Inclined surface 54 does not necessarily have to extendconically, either. For example, an equivalent, convexly arcuateconfiguration would be possible as well. Finally, the conditions may bereversed so to speak, i.e. the functionally necessary inclined surfacemay be provided on ring 50 and the counterpiece provided for linecontact only may be formed on clamping engagement bodies 51.

FIGS. 7 to 9 show an alternative embodiment of a piezoelectric drivemember. Similar parts are designated with the same reference numerals asin FIGS. 1 to 6.

Drive member 22 contains a first clamping means 38, a second clampingmeans 40 and the piezoelectric linear mover 36 disposed therebetween.The piezoelectric clamping member actuators 44 of first and secondclamping means 38, 40 as well as the linear mover 36 are attached inFIG. 7 above motion transmitting member 16. Drive member 22 has ahousing 70, e.g. of metal, having--seen from the left towards theright--supporting walls 72, 74, 76, 78 analogous with plates 41, 43, 45,47 of FIG. 2. Between supporting walls 74 and 76, linear mover 36 isheld without play. Supporting walls 76 and 78 as well as 72 and 74,respectively, each serve for supporting components of the first andsecond clamping means 38, 40, respectively. In the lower portion ofhousing 70, supporting walls 72, 74, 76 and 78 each have a rectangularopening 92 through which motion transmission member 16 extends.

Clamping member 48--corresponding in function to ring-like clampingmember 48 of FIGS. 2 to 6--of clamping means 38 has a base 87 abuttingwith its left face side with respect to FIG. 7 on supporting wall 76 andresiliently connected at its upper end to a finger-like clampingengagement body 51. Clamping engagement body 51 has a nose 84 forproviding support towards the top against housing 70 and carries at itsfree end the clamping surface 56. The clamping engagement body 51 intotal extends from above in inclined manner downwardly towards motiontransmitting member 16. By a flexurally soft connection 86 and aconnecting piece 88, clamping member 48 is fixedly connected to theleft-hand end of clamping member actuator 44. Clamping member actuator44 is supported by an adjusting screw 80 cooperating with a threadedportion of right-hand supporting wall 78. An intermediate piece 90protects clamping member actuator 44 against damages by adjusting screw80.

When clamping member actuator 44 is actuated, its left-hand end, via theflexurally soft connection 86, urges clamping surface 56 of clampingengagement body 51 against motion transmitting member 16, with nose 84preventing an evasion towards the top. Base plate 92 of housing 90 hasthe function of an abutment for motion transmitting member 16.

When flexurally soft connection 86, which transmits the force ofclamping member actuator 44, is displaced further upwardly in relationto the representation shown in FIG. 7, the pressing distance by whichclamping surface 56 moves towards motion transmitting member 16increases with a given stroke of clamping member actuator 4, while thepressing force transferred thereby decreases at the same time. Similarto the statements made with respect to FIGS. 5 and 6, a desired relationbetween pressing force and pressing distance can be chosen--in this caseby a suitable selection of inclination and leverage conditions.

As in FIG. 2, clamping means 38 and 40 are oriented in the samedirection. Adjustment screw 80 in second clamping means 40 cooperateswith clamping member 48. In the region of supporting wall 72, drivemember 22 is shown in a longitudinal section so that opening 92 insupporting wall 72 is visible, through which motion transmitting member16 extends.

In the cross-sectional view of FIG. 9, clamping member actuator 44extends across the entire width of housing 70 so that drive member 22 isconfined by housing 70, downwardly by base plate 92 and upwardly bycover plate 94. Between base plate 92 and clamping member actuator 44,motion transmitting member 16 is provided, which is in the form of aflat band of rectangular cross-section. The width of the flat band maybe chosen freely. In an extreme case, only an edge portion of motiontransmitting member 16 cooperates with drive member 22. Drive member 22then is slotted continuously on one side.

A cross-sectional view of drive member 22 in the region of piezoelectriclinear mover 36 is shown in FIG. 8. In this region, corner rods 100,102, 104, and 106 form an expandable, elastic connection between the twoclamping means 38, 40. Upper opening 98 and lower opening 96 areindicated in FIG. 7 in broken lines.

The function of this drive member 22 is analogous with that of drivemember 22 described in connection with FIGS. 2 to 6.

An embodiment according to FIG. 10 serves mainly for elucidating apreferred position determining means. Parts functionally correspondingto functional parts of the preceding embodiments are designated with thesame reference numerals as before.

As in the preceding embodiments, schematically shown drive member 22contains first clamping means 38, second clamping means 40 and thepiezoelectric linear mover 36 disposed therebetween. However, theclamping members indicated in the form of arrows 110 now are oriented inopposite directions and both arranged adjacent linear mover 36.

Motion transmitting member 16 in this embodiment consist, in the sectionof its length directly cooperating operating with drive member 22, of aflat band 16a (as elucidated with the embodiment according to FIGS. 7 to9), and in its remainder of a steel rope 16b soldered to band 16a at 112and extending to forward end 8 of movable section 4 of endoscope shaft2. At the opposite end of band 16a, a piece of guide wire 114 issoldered thereto. FIG. 10 shows the middle position of band 16a, fromwhich it is movable by means of drive member 22 by a movement distance116 both to the left and to the right.

One coil 118 each is attached both to the right-hand or forward end andto the left-hand or rearward end of drive member 22. In operation,alternating current flows through both coils 118, and their alternatingcurrent resistance will be determined for each case in an evaluationcircuit, with the alternating current resistance measured beingdependent upon the extent to which band 16a projects into the respectivecoil 118 in axial direction. In the illustrated middle position of band16a, the two ends thereof project only slightly into both coils 118.When band 16a now is moved e.g. to the right, the inductance ofright-hand coil 118 changes. By the afore-described resistancemeasurement of right-hand coil 118, it is possible to determine withgood accuracy by which distance band 16a has moved from the middleposition. Analogously therewith, band 16a may be moved from theillustrated middle position towards the left by drive member 22, withband 16a entering left-hand coil 118 with an increasing length and withthe position of band 16a being adapted to be determined by resistancemeasurement on left-hand coil 118.

The two coils 118, on their end facing away from drive member 22, eachhave an end wall 120 provided with a central small round opening 122.Steel rope 16b and guide wire 114, respectively, are adapted to extendthrough the respective opening 122, but not band 16a, whereby mechanicalend stops for movement of the band 16a and thus of the entire motiontransmitting member 16 are formed. Also the ends of coils 118 facingdrive member 22 have an end wall 124 with a through-opening 126 in thecentral portion. Through-openings 126, however, are of a size to permitpassage of band 16a. Guide wire 114, which in turn is guided in opening122 and/or opening 126, has the function of guiding the left-hand end ofband 16a, during movement thereof towards the left, properly back intoleft-hand coil 118.

When the two coils 118 have the same inductance or the same resistancemeasured, a detection signal of the position determining means is thuspresent to the effect that motion transmitting member is in its middleposition. When this signal is present for all three drive members 22,24, 26 (FIG. 1), movable section 4 is its straight position. Theevaluation circuit of coils 118 may have a path limiting circuitconnected thereto which interrupts the current supply to drive member 22as soon as band 16a has reached the left-hand or the right-hand endposition, so that band 16a does not move out of the clamping portions ofclamping means 38 and 40.

The evaluation circuit of coils 118, furthermore, may have a movementexamination circuit connected thereto. When band 16a, despite currentsupply to drive member 22, does not move an adequate distance, ablocking condition of motion transmitting member 16 against suchmovement is present. Continued operation of drive member 22 would resultin the formation of braking marks on band 16a in the engagement portionswith clamping means 38 and 40. In such a situation, the movementexamination circuit may interrupt the current supply to drive member 22.Band 16a then may be moved a small distance in the opposite direction;thereafter, a restart of the movement in the previously intendeddirection may be made.

Adjusting means or readjusting means for the rest position of clampingmeans 38 and 40 and thus for the play between clamping surfaces 56 andmotion transmitting member 16 in the unclamped condition as well as forthe pressing force between clamping surfaces 56 and motion transmittingmember 16 in the clamped condition are a preferred feature of drivemember 22 according to the invention. An example hereof are theadjusting screws 80 illustrated in FIG. 7.

We claim:
 1. An endoscope assembly with an endoscope shaft having amovable section in a front end portion, and having at least oneminiaturized piezoelectric drive member provided therein for moving themovable section via a motion-transmitting member, saidmotion-transmitting member including an elongated strand whichcooperates directly with the drive member; and said drive memberincluding two piezoelectrically-operable clamping members foralternating clamping engagement with the motion-transmitting member,each of said clamping members having a piezoelectric member and anengagement body which is inclined relative to the motion-transmittingmember, said engagement body being operable to pivot under the influenceof said piezoelectric member so as to provide a clamping engagement witha side of said motion-transmitting member.
 2. The endoscope assembly ofclaim 1 further including position-determining means for detecting theposition of the motion-transmitting member relative to the drive member.3. The endoscope assembly of claim 2 wherein said position-determiningmeans is electromotively operated.
 4. The endoscope assembly of claim 3wherein said position-determining means comprises a pair of coilsdisposed on opposite sides of said drive member.
 5. The endoscopeassembly of claim 1 further including means for cooling the drivemember.
 6. The endoscope assembly of claim 5 wherein said means forcooling comprises an evaporation cooling bath.
 7. The endoscope assemblyof claim 1 wherein said clamping members have an angle of inclinationrelative to said motion-transmitting member which is less than fortyfive degrees and which results in an amplification of a clamping forcetransmitted between said clamping members and said motion-transmittingmember.
 8. The endoscope assembly of claim 1 wherein the piezoelectricclamping members of the drive member are disposed on one side of themotion-transmitting member.
 9. The endoscope assembly of claim 1 whereinsaid endoscope shaft has three circumferentially spaced drive membersthereon.
 10. The endoscope assembly of claim 1 comprising a plurality ofdrive members disposed at the same longitudinal location relative tosaid endoscope shaft.
 11. The endoscope assembly of claim 1 comprising aplurality of drive members which are arranged in a longitudinallystaggered manner relative to said endoscope shaft.
 12. The endoscopeassembly of claim 1 comprising a drive member connected to said movablesection of said endoscope shaft so that said movable section can be bentat an angle relative to a remainder of said endoscope shaft.
 13. Theendoscope assembly of claim 1 comprising a drive member connected tosaid movable section of said endoscope shaft so that said movablesection is variable in length.
 14. A miniaturized piezoelectric lineardrive assembly for an endoscope shaft with a movable section in a frontend portion of the endoscope shaft, said assembly comprising:a) movablemeans for engaging said movable section of said endoscope shaft; b) apiezoelectric linear mover mounted on said movable means; and c) a pairof piezoelectrically operated clamping members mounted on said movablemeans on opposite sides of said linear mover, said clamping membersincluding a clamp engagement body which is inclined relative to saidmovable means and is operable to pivot under the effect of electriccurrent to establish a clamping engagement with said movable means, saidclamping members being operable to alternatingly clamp and release saidmovable means whereby a clamped one of said clamping members is operableto transmit motion to said movable means when engaged by said linearmover.